Final answer:
The DNS resource record for locating domain controllers and AD DS services is the Service (SRV) record, which provides the location of servers for specified services within an Active Directory environment.
Step-by-step explanation:
The special DNS resource record that enables clients to locate domain controllers and other vital Active Directory Domain Services (AD DS) services is the Service (SRV) record. SRV records are used in DNS to define the location, i.e., the hostname and port number, of servers for specified services. In the context of AD DS, SRV records are critical as they help clients find services like domain controllers, global catalogs, and other essential services within an Active Directory environment. When a computer joins a domain, it uses these SRV records to locate an Active Directory domain controller to authenticate and receive policy information.
For example, the LDAP services provided by AD DS can be found using an SRV record with the service type "_ldap". The naming convention for SRV records follows the pattern _Service._Proto.domain, where "_Service" specifies the name of the required service, "_Proto" specifies the protocol (such as _tcp or _udp), and "domain" specifies the domain name.